File ".10dir" serves for files allocation in subfoldersГ¬ "1-10..". It's useful if there are many files. At that first 10 files come to current folder. For example, file "122.mes" physically would be represented as file "_1/_2/2.mes". In the system it would look as "data-guestbook-_1-_2-2--mes".

System automatically creates files ".10next.mes" and ".lock".
Don't delete or edit them! You'll have a disturbance in working of system.